2009-06-08_REVISION - M1997032 (25)

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Hydrogeological Evaluation of Van 4 Mine Geologic and Hydrogeologic Conditions Exhibit 2-2. Definition of Local Hydrogeologic Units in Vicinity of the Van 4 Mine. Hydrogeologic Unit Local Description Defined by Weir et al. Hydrologic (1983) Unit Mesozoic Aquifer Navajo Aquifer Aquifer contains saturated portions of the Cutler Formation, Chinle Formation, Wingate Sandstone, Kayenta Formation, Navajo Sandstone, and Entrada Sandstone. The aquifer is overlain by shale of the Summerville Formation, and underlain by rock salt of the Paradox Member of the Hermosa Formation. Salt Wash Aquifer includes the saturated portions of the Saltwash Aquifer Member of the Morrison Formation. This aquifer is overlain by bentonitic shales of the Brushy Basin Member of the Morrison Formation and is underlain by shale of the Summerville Formation. Tertiary to Upper Dakota Aquifer Aquifer contains the saturated portion of the Dakota Cretaceous aquifer Sandstone and the Burro Canyon Formation. It is overlain by the Mancos Shale and underlain by shale of the Brushy Basin member of the Morrison Formation. Mesaverde Not present in the vicinity of the Van 4 Mine. Aquifer • An aquifer includes only the saturated portion of the respective geological units. Mr. Jon Showalter (Denison Project Geologist, personal communication 2008) reports that a small amount of seepage is present at the base of the Burro Canyon Formation in the area of the Van 4 Mine. Where saturated, the Burro Canyon Formation is a part of the Dakota Aquifer. Cater (1954) does not indicate the presence of springs at the base of the Burro Canyon Formation; however, springs may be present at this contact on a local or seasonal basis that were not identified by Cater (1954). The available data suggest that saturated conditions may be present on a local or seasonal basis at the base of the Burro Canyon Member, but that groundwater within this unit is relatively limited. The Burro Canyon Formation is underlain by the Brushy Basin member of the Morrison Formation, which is a confining layer. The bentonitic shale of the Brushy Basin Member restricts downward percolation of groundwater from the overlying Burro Canyon Formation. The Brushy Basin Shale is underlain by the Salt Wash Member of the Morrison Formation. The Van 4 mine underground workings are located within the upper portion of the Salt Wash Member. Where saturated, this unit forms the Salt Wash aquifer. As described previously, the Van 4 mine underground workings are not currently accessible. However, the underground workings are reported to be dry (J. Showalter, Denison project geologist, personal communication 2008), which suggests that saturated conditions are not present in the mine area. 2-9 draft final van 4 hydmgeology report.doc